1. Field of the Invention
The present invention relates to a display device in which pixels are constituted by two lines of picture elements connected to a single gate wiring, and more particularly, to a display device that makes luminance unevenness less likely to occur by the array of picture elements, even when inversion driving is performed.
2. Description of the Related Art
In recent years, flat display devices such as liquid crystal display devices and EL display devices characterized by having low power consumption and being slim and lightweight have been widely used as display devices such as television receivers. With flat panels such as liquid crystal panels and EL panels used in flat display devices, image display is normally performed with a driving method called an active matrix method. This active matrix method involves displaying an image by selecting and driving TFTs, which are switching elements formed in each of a plurality of picture elements arrayed in a line direction and a column direction, depending on signals from gate wirings disposed along the line direction and source wirings disposed along the column direction, to control the luminance of each of the picture elements.
Adverse effects such as degradation of a liquid crystal layer or an EL layer being caused or responsiveness to image signals deteriorating when image signals are continuously applied at the same polarity are known to occur with liquid crystal panels and EL panels used in flat display devices. So-called inversion driving is thus performed whereby, whenever a signal for displaying an image is input, driving is performed after inverting the polarity of the signal. This operation of inverting the polarity of an image display signal is called frame inversion driving if performed with regard to the picture elements of the entire panel constituting a single screen, line inversion driving if performed for each line formed by picture elements, and dot inversion driving if performed for each adjoining picture element.
Conventionally, a technique is known for realizing the above-described inversion driving while using a so-called center gate method, which is a technique for connecting two lines of picture elements to a single gate wiring, and increasing the time for which an image display signal is applied to the TFT formed in each picture element, in an active matrix type liquid crystal panel serving as a display element (JP 2001-33757A).
FIG. 14 is a main portion enlarged view showing the configuration of an image display area 101 of such a conventional liquid crystal panel 100.
As shown in FIG. 14, in the image display area 101 of this conventional liquid crystal panel 100, a single pixel 102 is constituted by disposing four picture elements 103 consisting of red (R), blue (B) and two green (G1, G2) picture elements in two lines in a longitudinal direction and two columns in a lateral direction. A gate wiring 105 is disposed along the lines of picture elements, between the first line to which the R and G1 picture elements belong and the second line to which the B and G2 picture elements belong. Also, two source wirings 106 are disposed for each column of picture elements 103, so as to sandwich each picture element 103 laterally.
With the liquid crystal panel 100 shown in FIG. 14, respective picture elements in the same position in laterally adjoining pixels 102 are connected to source wirings on different sides. For example, with the pixels 102 positioned on the left side in FIG. 14, the R picture elements are connected to the source wiring 106 that is on the left side of the column of picture elements 103 and has positive polarity data applied thereto, whereas with the pixels 102 positioned on the right side, the same R picture elements are connected to the source wiring 106 that is on the right side of the column of picture elements 103 and has negative polarity data applied thereto. Note that with the pixels 102 lined up in the longitudinal direction, same color picture elements 103 in the same position are all connected to the same source wiring 106.
In each picture element 103, a TFT 104, which is a switching element for driving, is connected to the gate wiring 105 and the source wiring 106 to which that picture element 103 is connected. Also, the gate wirings 105 are sequentially selected by a gate driver 107, and the source wirings 106 are connected to a source driver 108 and apply signals for image display to the TFTs 104 of the picture elements 103 connected to a selected gate wiring 105.
Thus, with the conventional liquid crystal panel shown in FIG. 14, since same color picture elements disposed in the same position in laterally adjoining pixels are connected to source wirings to which different polarity data is applied, the polarity of adjoining picture elements for displaying an image will be inverted even in the case where a monochromatic screen is displayed. Accordingly, a luminance difference produced by the polarities of the voltages applied to the liquid crystal layer will be canceled, enabling the occurrence of flicker to be effectively reduced, even in the case of monochromatic image display.
In recent years, multi-primary color image display using multi-primary color picture elements has been performed, in order to expand the color reproduction range of flat panels. This multi-primary color image display involves constructing a single pixel with a combination of light from picture elements of four or more colors, by forming picture elements of not only the three colors RGB used in normal color display but also a white (W) picture element or picture elements of cyan (C), magenta (M) and yellow (Y) that are in a complementary color relationship with the three RGB colors, for example. At this time, because the shape of a pixel desirably is point-like more than linear, normally a single pixel is constituted in the form of two lines and three columns if six colors and two lines and two columns if four colors, rather than arranging the multi-primary color picture elements in one line to form a single pixel.
In the case where a single pixel is constituted by two lines of picture elements, the problem of a signal writing time to the driving TFT disposed in each picture element being shortened, due to not increasing the number of gate wirings as a result of applying a technique of driving two lines of picture elements with a single gate wiring as shown as the above conventional technique, is thus avoided.
However, the occurrence of streaky luminance unevenness on the display screen has been confirmed, in the case where inversion driving such as dot inversion driving or line inversion driving is performed, while sequentially selecting and scanning two lines of picture elements using a single gate wiring, in multi-primary color image display.